Jailed Iranian trade unionist Reza Shahabi was temporarily released on bail late on Monday night following more than three weeks on hunger strike.
The Tehran bus workers' union Vahed treasurer was let out of prison for five days to address his health problems.
Mr Shahabi was released from Evin prison at around 10.30pm without any prior notification. He ended his 23-day hunger strike when he got home to his family an hour later.
He has been in jail since June 2010 when he was sentenced to six years in prison, a five-year ban on union activity and a £3,500 fine.
Mr Shahabi was severely beaten during his interrogation and his health has deteriorated massively.
He underwent major surgery on his neck and spine last August with doctors saying he needed at least two months rest at home and was "incable of withstanding any further punishment."
Despite that he was hauled back to the notorious Ward 350 of Evin jail, used to house "political" prisoners following a 2010 post-election crackdown on labour and rights activists.
Inmates claim that dissident blogger Sattar Beheshti was severely beaten there by Iranian security services in November shortly before his death.
On December 15 Mr Shahabi was taken to hospital but guards refused to allow him proper examination and forced him back to the prison with threats of beatings and insults.
Five more political prisoners joined his hunger strike on January 5 in support of his demand for proper access to medical care.
Iran solidarity group Codir assistant general secretary Jamshid Ahmadi urged people to keep up the international campaign for Mr Shahabi and other political prisoners' release.
The International Transport Workers Federation, French union confederation CGT, Canadian union Cupe, Britain's TUC and many other international workers' bodies have demanded his release.
"It is obvious that the international campaign for his release and improvement of his conditions has played a significant part," said Mr Ahmadi.
"Reza Shabi should not be returned to prison. He is a trade unionist and has not committed any wrong except campaigning for the rights of workers."
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